Field of the Invention
The present invention relates to a sheet transport apparatus that includes a plurality of transport paths and a movable guide portion, which guides in such a manner as to perform switching of a transport path along which a sheet is to be transported, and an image forming apparatus.
Description of the Related Art
In general, in an image forming apparatus that employs an electrophotographic system, a configuration is employed in which a toner image, which has been transferred to a sheet by a transfer unit, is fixed onto the sheet by a fixing unit. In the related art, there has been a problem in that a sheet becomes stuck in a transport path (such a phenomenon will hereinafter be referred to as a paper jam) as a result of condensation occurring in an apparatus and in the transport path caused by steam generated by the sheet, to which a toner image has been fixed by a fixing unit. There is known a method of causing air to flow across a transport path, which is used after a toner image has been fixed to a sheet, by disposing an air-blowing fan and an exhaust duct in the transport path and guiding steam to an exhaust duct so as to discharge the steam outside the apparatus in order to prevent the occurrence of a paper jam (Japanese Patent Laid-Open No. 2008-90198).
In addition, there is known a method of holding back steam by using a discharge preventing member and exhausting, by blowing air, steam that has collected in a transport path between a fixing unit and the discharge preventing member in order to prevent the steam from diffusing from an air-blowing exhaust area (Japanese Patent Laid-Open No. 2008-90199).
Furthermore, an apparatus in which a flow-control unit is disposed in such a manner as to face an air-discharge port of an air-cooling unit in order to cool a sheet, to which a toner image has been fixed, the flow-control unit being configured to perform switching of a flow path of air from an air-blowing unit in accordance with an image forming mode for the sheet (two-side mode or normal mode), is disclosed in Japanese Patent Laid-Open No. 2001-255807.
However, in the case where there are a plurality of transport paths used for transporting a sheet, to which a toner image has been fixed, it is necessary to dispose an air-blowing fan and an exhaust duct in each of the transport paths or to dispose communication ducts that connect the plurality of transport paths, an air-blowing fan, and an exhaust duct. If the communication ducts of the plurality of transport paths are in constant communication with the air-blowing fan and the exhaust duct, air will also flow into some of the transport paths that are not used. In the apparatus disclosed in Japanese Patent Laid-Open No. 2001-255807, the air flow path is switched by causing a separation claw member of the flow-control unit to rotate, and the separation claw member is brought into contact with a guide of a transport path, the transport path being formed as a result of a transport path branching into portions. Thus, the air also flows into one of the transport paths that is not used, that is, a transport path along which a sheet is not transported (see FIG. 2 of Japanese Patent Laid-Open No. 2001-255807). Therefore, in order to blow a sufficient amount of air into one of the transport paths that is being used, it is necessary to consider the amount of the air that will flow into the transport path that is not used and to blow more air than necessary, and consequently, the power and the size of the air-blowing fan need to be increased. In other words, there has been a problem in that, when trying to blow air, which is sufficient to exhaust steam, into a plurality of transport paths, the manufacturing costs and the size of an apparatus increase.
The present invention is directed at a sheet transport apparatus that includes a plurality of transport paths and that is capable of blowing air into the plurality of transport paths by employing a simple configuration.